Mo Ichido Papa to Yoba Reru hi

Mikura Kenji is a husband and father who suffers with anterograde amnesia, which prevents him from making new memories. Worried that his condition will be a burden on his family, he asks his wife for a divorce and leaves without so much as a word to his children about his illness. Two years later, Kenji learns about the death of his former wife and decides to try and raise his children as a single father, while depending on the diary she left behind.
(Source: Japanese = Natalie.mu || Translation = Drama-Otaku.com)